An optical disk player and a system for detecting accelerations of the optical disc player

FIELD OF THE INVENTION

This invention relates to an Optical disc player comprising: an optical pickup unit for reading the optical disc, the optical pickup unit comprising: - a lens, a lens actuator for positioning the lens,

BACKGROUND OF THE INVENTION

Such an optical disc player as commonly used in a personal computer or audio/video equipment.

Such an optical disc player has an optical pickup unit, commonly implemented as a single unit that allows the optical beam to be projected on the optical disc and the reflecting beam to be detected. In order to properly follow the track on the optical disc the optical pick up unit comprises not only all the elements needed to project and detect the optical beam but also needs means to ensure that the optical beam is properly focused on the track and properly tracks the track. For this the optical pickup unit further comprises a lens actuator, a detector for detecting a lens positioning error and a servo loop for controlling the lens actuator. It is not possible to fix the focus and the tracking of the optical beam because the optical disc is not perfectly flat, nor is it perfectly round and centered. Hence a servo loop is needed to actuate the lens actuator and thus keep the optical beam properly focused and tracking the track. Many methods are known to achieve this and these methods are often dependent on the actual implementation of the lens actuator. Since the servo loop dynamically adjusts the optical beam it also, within limits, adjusts for mechanical shocks the optical disc player experiences during operation. For instance, when a mechanical shock causes the optical beam to go out of focus the servo loop adjusts focus in order to regain focus. The servo loop merely detects a focusing error and corrects it.

SUMMARY OF THE INVENTION

It is an objective of the invention to provide such a player with additional functionality.

To achieve this objective the optical disc player is characterized in that the optical disc player comprises a means for deriving an acceleration measurement representing an acceleration of the optical disc player from the lens actuator and an interface means for providing the acceleration measurement to an external device.

When the entire optical disc player experiences an acceleration the lens actuator and lens also experience this acceleration. Due to the weak coupling to the rest of the optical disc drive and its own mass the lens actuator will lag the acceleration of the rest of the optical disc drive. This lag can easily be detected in various ways and provides information on the magnitude and direction of the acceleration optical drive relative to the lens actuator. Consequently a new functionality is added to the optical disc drive: the ability to provide acceleration information

In an embodiment of the optical disc drive the means for deriving an acceleration measurement comprises means for measuring a counter electromotive force originating from the lens actuator.

When the optical disc drive is idling no active correction of the lens actuator position is performed and the lens actuator, together with the attached coils is suspended in a magnetic field. When the lens actuator moves relative to the optical disc drive it moves inside the magnetic field which will cause a counter electromotive force which can be easily detected using methods well known to the skilled person.

In an embodiment of the optical disc drive the means for deriving an acceleration measurement comprises: a detector for detecting a lens positioning error, - a servo loop coupled to the detector for receiving the lens positioning error and for controlling the lens actuator in order to reduce the lens positioning error, lens positioning error and means for deriving the acceleration measurement from the lens positioning error.

When the entire optical disc player experiences an acceleration while actively reading or writing an optical disc, the lens actuator and lens also experience this acceleration and the servo loop for controlling the lens actuator will try to correct it. This unexpected correction can easily be detected and provides information on the magnitude and direction of the acceleration of the lens actuator and hence of the entire optical disc drive. Consequently a

new functionality is added to the optical disc drive: the ability to provide acceleration information.

In an embodiment of the optical disc player the optical disc player comprises mounting means for mechanically attaching the optical disc player to the external device. By attaching the optical disc drive to an external device the optical disc drive will experience the same mechanical accelerations as the external device and the acceleration information provided by the optical disc drive will also be representative for the external device it is attached to.

In a further embodiment of the optical disc player the lens positioning error is a focusing error.

By deriving the acceleration information from the focusing error, the optical disc drive is able to provide acceleration information about accelerations experienced along an axis parallel to the direction of focusing, i.e. in general perpendicular to the optical disc being read or written. In a further embodiment of the optical disc player the lens positioning error is a tracking error.

By deriving the acceleration information from the tracking error, the optical disc drive is able to provide acceleration information about accelerations experienced perpendicular to or along the direction of the track being followed, i.e. in a radial or lateral direction in a plane parallel to the optical disc being read or written.

In a further embodiment of the optical disc player the lens actuator allows the actuation of the lens in a further dimension and the means for deriving an acceleration measurement is arranged to derive a further acceleration measurement for the further dimension. Current actuators allow the movement of the actuator in four directions independently of each other and as such also allow the detection of an acceleration in all four directions.

In a further embodiment of the optical disc player the mounting means are positioned such that the acceleration measurement is associated to a particular acceleration of the external device. Even when the directions of detection are fixed relative to the housing of the optical disc drive by the positioning of the lens actuator in relation to the enclosure of the optical disc drive, the mounting position f the optical disc drive can be changed relative to the external device to match a desirable direction of detection of the acceleration of the external device.

In a further embodiment of the optical disc player the mounting means is arranged for attaching the optical disc player to an automobile.

By providing mounting means that allow attaching the optical disc drive to an automobile the optical disc drive can derive acceleration information about the automobile. In a further embodiment of the optical disc player the interface means are arranged to provide the acceleration measurement to a means for adjusting a suspension of the automobile.

When the optical disc drive detects shocks (accelerations) of the automobile exceeding a predefined level when driving the suspension is not adjusted soft enough. This acceleration information provided by the optical disc drive is then used by the suspension system to adjust the suspension to reduce the shocks reaching the optical disc drive. This will not only improve the focusing and tracking of the optical disc by the optical disc drive but also improve the experience of the passengers of the car with respect to the comfort level of the car. Currently expensive acceleration sensors have to be used for this while the same functionality can be provided by the optical disc drive in the automobile.

A system comprising the optical disc player and the external device provides added value since acceleration to the external device is available without the use of expensive acceleration sensors.

In an embodiment of the system, the system is an earth quake detection system arranged to utilize the acceleration measurement and the external device is an earthquake detector.

An optical disc drive being able to detect acceleration is also able to detect the acceleration caused by an earth quake. The information can be provided to an external device where the optical disc drive is coupled to and processed by this external device. In a further embodiment of the system the optical disc player is mechanically attached to the external device.

By attaching the optical disc drive to an external device the optical disc drive will experience the same mechanical accelerations as the external device and the acceleration information provided by the optical disc drive will also be representative for the external device it is attached to.

In a further embodiment of the system the lens positioning error is a focusing error.

By deriving the acceleration information from the focusing error, the optical disc drive is able to provide acceleration information about accelerations experienced along

an axis parallel to the direction of focusing, i.e. in general perpendicular to the optical disc being read or written.

In a further embodiment of the system the lens positioning error is a tracking error. By deriving the acceleration information from the tracking error, the optical disc drive is able to provide acceleration information about accelerations experienced perpendicular to or along the direction of the track being followed, i.e. in a radial or lateral direction in a plane parallel to the optical disc being read or written.

In a further embodiment of the system the lens actuator allows the actuation of the lens in a further dimension and the means for deriving a acceleration measurement is arranged to derive a further acceleration measurement for the further dimension.

Current actuators allow the movement of the actuator in four directions independently of each other and as such also allow the detection of an acceleration in all four directions. In a further embodiment of the system the mounting means are positioned such that the acceleration measurement is associated to a particular acceleration of the external device.

Even when the directions of detection are fixed relative to the housing of the optical disc drive by the positioning of the lens actuator in relation to the enclosure of the optical disc drive, the mounting position f the optical disc drive can be changed relative to the external device to match a desirable direction of detection of the acceleration of the external device.

In a further embodiment of the system the external device is an automobile.

By providing mounting means that allow attaching the optical disc drive to an automobile the optical disc drive can derive acceleration information about the automobile.

In a further embodiment of the system the automobile comprises an adjustment means for adjusting a suspension of the automobile in response to the acceleration measurement provided by the optical disc player.

When the optical disc drive detects shocks (accelerations) of the automobile exceeding a predefined level when driving the suspension is not adjusted soft enough. This acceleration information provided by the optical disc drive is then used by the suspension system to adjust the suspension to reduce the shocks reaching the optical disc drive. This will not only improve the focusing and tracking of the optical disc by the optical disc drive but also improve the experience of the passengers of the car with respect to the

comfort level of the car. Currently expensive acceleration sensors have to be used for this while the same functionality can be provided by the optical disc drive in the automobile. In a further embodiment of the system the automobile comprises an airbag firing means for deploying an airbag in response to the acceleration measurement provided by the optical disc player.

A negative acceleration, i.e. deceleration, of the automobile can also be detected and when exceeding a predefined value the airbag can be triggered.

Since the acceleration can be determined in multiple dimensions and in real time it is possible to more accurately tune the firing of the airbags in the automobile to the actual experienced accelerations experienced by the automobile. It should be further noted that for airbag safety multiple sensors are required in each direction to make the system fail safe. The addition of the acceleration information by the optical disc drive enhances the safety of such airbag systems without increasing the cost since no additional acceleration sensors are needed. In a further embodiment of the system the automobile comprises means for adjusting an Anti-lock Braking System in response to the acceleration measurement provided by the optical disc player. During a substantial breaking effort the car experiences decelerations which can be sensed by the optical disc drive and the detected acceleration information can be provided the anti-lock braking system. In a further embodiment of the system the automobile comprises means for adjusting a Traction Control System in response to the acceleration measurement provided by the optical disc player. A Traction Control System is meant to allow the automobile to accelerate in a controlled fashion on a slippery surface. Acceleration in an unexpected direction provides important information to the system providing feedback about the condition of the road. Even when the wheel does not spin due to the usual Traction Control the automobile might still start moving (slipping) in an undesirable direction which the current Traction Control Systems might not notice. The acceleration information provided by the optical disc drive provides this extra information allowing the Traction Control System to react and correct. In a further embodiment of the system the external device is a personal computer.

The optical disc drive is a common part of a personal computer. When the personal computer is moved while the hard disk is running the hard disk may be damaged by accelerations. A detection of acceleration of the personal computer can be used to avoid

damage to hard disk. A detection of acceleration of the personal computer can also be used to detect unauthorized movement of the person computer, for instance theft of the personal computer or attempts to open the personal computer.

In a further embodiment of the system the personal computer comprises responding means for responding to the acceleration measurement provided by the optical disc player.

For instance when theft or unauthorized opening is suspected a message can be dispatched to security personnel so that they can appropriately respond to the situation.

In a further embodiment of the system the responding means is arranged to prevent damage to the personal computer.

When an acceleration is detected a warning can be given.

In a further embodiment of the system the damage is damage to the hard disk and the responding means is arranged to lock a head of the hard disk when the acceleration measurement exceeds a preset limit. By locking the hard disk head when the acceleration experienced exceeds a preset limit the hard disk is protected. Currently acceleration sensors are required while the optical disc drive can also provide the acceleration information.

In a further embodiment of the system the responding means is an alarming means form alarming service personnel that the personal computer has experienced an acceleration exceeding a preset limit.

Just logging the experienced accelerations and informing service personnel allows the service personnel to perform preventive service such as the replacement of a hard disk when the personal computer has experienced a hard shock. The hard disk is likely to be damaged and future data loss can be prevented by a replacement of the hard disk by a new one.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described based on figures. Figure 1 shows a conventional optical disk drive. Figure 2 shows an optical disc drive comprising the invention.

Figure 3 shows a lens actuator. Figure 4 shows an lens carrier.

Figure 5 shows an vibration detection system according to the invention. Figure 6 shows an automobile according to the invention.

Figure 7 shows a personal computer according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 shows a conventional optical disk drive. The optical disc drive 1 comprises a central processor 10 interfacing with external device through the input 5 and the output 9 of the optical disc drive.

Figure 1 shows the optical disc drive 1 in read mode but the following also applies to the optical disc drive in write mode.

The optical disc 2 is illuminated with an optical beam passing the mirror 8 and passing through the lens 4 before reaching the optical disc and originating from the laser diode in the driver electronics 12 in the optical pickup unit 14. The reflected beam passes through the lens 4 and is reflected by the mirror 8 towards the photo detector 3. The information retrieved by the photo detector 3 is used to retrieve both data information and focusing and tracking errors. The focusing and tracking errors are not interesting for the outside world and remain within the optical disc drive 1. Within the optical disc drive 1 the focus and tracking errors are sent to the respective servo loop in the servo processor 11. The servo processor 11 provides the signals that allow the driver electronics 12 to correct and minimize the focus and tracking errors. For this the driver electronics 12 sends its output signals to the actuator 7 which manipulates the position of the lens 4 in response to the output signals of the drive electronics.

Figure 2 shows an optical disc drive comprising the invention.

In addition to the conventional optical disc drive the servo processor 11 not only provides corrective signals to the driver electronics 12 but also acceleration information derived from the error signals to the central processor which in turn can provide the acceleration information to an external device either via a special output interface 13 or through the regular output 9 of the optical disc drive.

When the optical disc drive 1 experiences a shock, i.e. acceleration, for instance in the vertical direction of figure 2 downward the lens 4 would lag because of its mass. The distance between the optical disc 2, which will move down along with the optical disc drive 1, and the lens 4, which lacks this strong mechanical connection and is suspended in a magnetic field, would be decreased. This decrease in distance results in a focus error detected by the photo detector 3. The servo processor 11 will detect this decrease in distance and will send corrective signals to the driver electronics 12. In addition, information about

this decrease in distance will be provided tot the central processor 10 or an additional dedicated processor (not shown) if a faster response time is desirable.

Since predictive focusing and tracking is common, the servo processor 11 knows what the focus and tracking signals approximately should look like at any given time and as such can distinguish very well between corrections needed because the optical disc isn't perfectly flat and centered, which have a repetitive nature linked to a single revolution of the optical disc, and true accelerations due to external influences.

Figure 3 shows a lens actuator.

The lens actuator 30 is part of the optical pickup unit 14 in figure 1 and figure 2 and comprises a body 36 for mounting the lens actuator to the optical pickup unit.

The lens actuator 30 shown allows the movement of the lens 33 in multiple directions. To this end the lens actuator comprises two magnets 31, 31a, and a lens carrier 34 comprising the lens 33 and several coils 35 in the front and several coils 32 in the back of the lens carrier 34. The coils 32, 35 allow the creation of a magnetic field which in combination with the permanent magnets 31, 31a allow the lens carrier 34 to be moved in various directions, i.e. upward/downward for focusing, left/right for radial tracking, forward/backwards for lateral tracking and a rotation for tilting the lens carrier 34.

It should be noted that the shown lens actuator is only used for illustration and that any other lens actuator can be used with the invention as the invention does not lie in the construction of the actuator itself.

When the optical disc drive 1 experiences an acceleration the body 36 of the lens actuator 30 will also experience this acceleration and move in the way as the optical disc drive 1 because it is mechanically coupled to the optical disc drive 1. The lens carrier 34 will however, because of its mass, lag, causing the focus or tracking to be affected or even lost. To correct this the servo processor 11 will cause the driver electronics 12 to send correcting currents through the coils 32, 35 to restore correct focus or tracking. In addition to this corrective action the servo processor 11 will send the acceleration information to the central processor 10.

Figure 4 shows a lens carrier. Compared to figure 3, in figure 4 the actuator body 36 has been removed to reveal a better view of the lens carrier 34 and the front coils 35a, 35b, 35c.

The lens carrier is suspended by thin springs that position the lens carrier in a resting position when no currents are applies to the coils and allow movement of the lens carrier 34 when the coils interact with the permanent magnetic field.

Position anchor 39 forms a base where the springs are affixed to the actuator body 36.

Figure 5 shows an vibration detection system according to the invention.

In an area 51 an vibration occurs, for instance stemming from an earth quake or from a person walking around. This results in shock waves 55 a, 55b traveling through the area 51. In the area 51 one or more devices 52a, 52b, 52c comprising an optical disc drive 53a, 53b, 53c are located. The devices 52a, 52b, 52c can for instance be personal computers in a building or spread over a large area.

The optical disc drives 53a, 53b, 53c are capable of detecting accelerations and providing this acceleration information to a centralized device 54 where the acceleration information can be processed.

When the positions of the devices 52a, 52b, 52c are known it is not only possible to judge the magnitude of the acceleration but also to use triangulation to pin point the exact source of the vibrations causing the acceleration of the devices 52a, 52b, 52c. By gathering the mechanical acceleration/de-acceleration information of multiple optical disc drives 53a, 53b, 53c (e.g. via internet), coupled with the physical location of the drive, an earthquake can be detected. Because so many PCs are on all the time there will always be a dense network of measurement points allowing a more detailed evaluation/ prediction. Alternatively each device 52a, 52b, 52c can store the acceleration information together with the exact time of occurrence allowing the later retrieval of this data for evaluation or can cause a local alert if desired.

Figure 6 shows an automobile according to the invention.

The automobile 60 comprises front wheels 65 a and rear wheels 65b and an active suspension system 66a, 66b, 67 comprising front suspension elements 65a, rear suspension elements 65b and an active suspension controller 67. Normally the active suspension controller 67 derives the acceleration information from expensive acceleration sensors (not shown). In the present invention an optical disc drive 61 is mounted in the automobile 60 and is subject to the same acceleration as the automobile 60. Also shown in figure 6 are the optical disc 62 and the lens actuator 63 in the optical disc drive. Any shock caused by the road 64 or other external influence is transmitted via the wheels 65 a, 65b and the suspension elements 66a, 66b to the chassis of the automobile 60. Because the optical disc drive 61 is mounted to the chassis of the automobile 60 any acceleration of the chassis is also transmitted to the optical disc drive 61. As explained above the mass of the lens actuator

causes the lens carrier to lag the acceleration of the optical disc drive and thus allows the detection of the acceleration. This acceleration information is subsequently provided to the active suspension controller 67. The active suspension controller 67 reacts by adjusting the active suspension to take into account the acceleration information, for instance by adjusting the active suspension until acceptable acceleration information is received from the optical disc drive 61.

Figure 7 shows a personal computer according to the invention. The personal computer 70, for instance a laptop, comprises a hard disk 73, a processor 72, and an optical disc drive 71 according to the invention. When the optical disc drive detects an acceleration that may be harmful for the hard disk 73 it sends the acceleration information to the processor 72. The processor 72 subsequently instructs the hard disk 73 to retract the head quickly to the parking zone and, if possible, lock the head in this position. When a laptop 70 for instance falls off a table while the laptop 70 is powered up, the initial acceleration exceeds a preset threshold causing the protection mechanism described above to be activated. When the laptop 70 experiences the much larger deceleration upon impact with the floor the hard disk 73 has already safely been parked and harm to the laptop 70 is minimized. Since most personal computers 70 and many other devices comprising a hard disk 73 also comprise an optical disc drive 71, no additional acceleration sensors are needed because the optical disc drive 71 can provide the required acceleration information in three dimensions with minimal additional cost.